Exhaust Fan Venting - Bathroom, ERV, & HRV - Home Energy Pros2015-03-31T22:04:25Zhttp://homeenergypros.lbl.gov/forum/topics/exhaust-fan-venting-bathroom-erv-hrv?groupUrl=bestpracticesresidential&commentId=6069565%3AComment%3A95373&groupId=6069565%3AGroup%3A2238&feed=yes&xn_auth=noNow, if you really want to "s…tag:homeenergypros.lbl.gov,2012-10-10:6069565:Comment:962302012-10-10T14:22:45.481ZRobert Riversonghttp://homeenergypros.lbl.gov/profile/RobertRiversong
<p>Now, if you really want to "stack" the variables, consider that the outside air is dynamic, with falling high pressure ridges and rising low pressure troughs, falling air becoming warmer and rising air becoming cooler (yes, meteorologists speak of rising warm air columns), and wind dynamics....</p>
<p>Now, if you really want to "stack" the variables, consider that the outside air is dynamic, with falling high pressure ridges and rising low pressure troughs, falling air becoming warmer and rising air becoming cooler (yes, meteorologists speak of rising warm air columns), and wind dynamics....</p> Robert wrote:"John, I think y…tag:homeenergypros.lbl.gov,2012-10-10:6069565:Comment:963352012-10-10T10:52:01.066ZJohn Brookshttp://homeenergypros.lbl.gov/profile/JohnBrooks
<p>Robert wrote:"John, I think you're overthinking this passive NPP issue...."</p>
<p>Robert, I know ... I am aware of my stacking disease....…</p>
<p><a href="http://api.ning.com:80/files/esFmm3irP*mham-pK9bADFhZ9ObkGAveCPFs94ztKfc33wDMVXwurtwftdMEuKh*yyv4Y6KGRcKdCt8h*0kxYgqtKQibB5mC/stacking.jpg" target="_self"><img class="align-full" src="http://api.ning.com:80/files/esFmm3irP*mham-pK9bADFhZ9ObkGAveCPFs94ztKfc33wDMVXwurtwftdMEuKh*yyv4Y6KGRcKdCt8h*0kxYgqtKQibB5mC/stacking.jpg" width="562"></img></a> <a href="http://api.ning.com:80/files/CNnp1xqiJxJEnHBuu7IfxqEW6NOpm5t*AdOZ3qsHdThXHt7j8pQV2Y5y93gNyy4f2kkOEU42kkLH2chQIDgUjtZopFYzXfN3/st.JPG" target="_self"><img class="align-full" src="http://api.ning.com:80/files/CNnp1xqiJxJEnHBuu7IfxqEW6NOpm5t*AdOZ3qsHdThXHt7j8pQV2Y5y93gNyy4f2kkOEU42kkLH2chQIDgUjtZopFYzXfN3/st.JPG?width=721" width="721"></img></a></p>
<p>Robert wrote:"John, I think you're overthinking this passive NPP issue...."</p>
<p>Robert, I know ... I am aware of my stacking disease....</p>
<p><a href="http://api.ning.com:80/files/esFmm3irP*mham-pK9bADFhZ9ObkGAveCPFs94ztKfc33wDMVXwurtwftdMEuKh*yyv4Y6KGRcKdCt8h*0kxYgqtKQibB5mC/stacking.jpg" target="_self"><img class="align-full" src="http://api.ning.com:80/files/esFmm3irP*mham-pK9bADFhZ9ObkGAveCPFs94ztKfc33wDMVXwurtwftdMEuKh*yyv4Y6KGRcKdCt8h*0kxYgqtKQibB5mC/stacking.jpg" width="562"/></a><a href="http://api.ning.com:80/files/CNnp1xqiJxJEnHBuu7IfxqEW6NOpm5t*AdOZ3qsHdThXHt7j8pQV2Y5y93gNyy4f2kkOEU42kkLH2chQIDgUjtZopFYzXfN3/st.JPG" target="_self"><img class="align-full" src="http://api.ning.com:80/files/CNnp1xqiJxJEnHBuu7IfxqEW6NOpm5t*AdOZ3qsHdThXHt7j8pQV2Y5y93gNyy4f2kkOEU42kkLH2chQIDgUjtZopFYzXfN3/st.JPG?width=721" width="721"/></a></p>
<p> </p> Great insights for cold clima…tag:homeenergypros.lbl.gov,2012-10-04:6069565:Comment:958222012-10-04T18:56:04.230ZRobert Riversonghttp://homeenergypros.lbl.gov/profile/RobertRiversong
<p>Great insights for cold climates. Few in the industry, even in cold climate zones, appreciate the damage that ice dams can cause. For that reason, I am as much a proponent of attic/roof ventilation as for indoor ventilation to avoid moisture problems.</p>
<p>Great insights for cold climates. Few in the industry, even in cold climate zones, appreciate the damage that ice dams can cause. For that reason, I am as much a proponent of attic/roof ventilation as for indoor ventilation to avoid moisture problems.</p> I would like to share some of…tag:homeenergypros.lbl.gov,2012-10-04:6069565:Comment:956412012-10-04T18:27:10.866ZPaul Morinhttp://homeenergypros.lbl.gov/profile/PaulMorin
<p>I would like to share some of the lessons learned by the Minneapolis Sound Insulation Program when it weatherized over 8000 homes near the MSP airport and installed continuously operating exhaust only ventilation in almost all of them. We are known for our extreme winters up here, so the problems we experienced may not show themselves as dramatically in milder locations but the building science is the same. </p>
<p> </p>
<p>When you have a continuously operating fan with a roof termination…</p>
<p>I would like to share some of the lessons learned by the Minneapolis Sound Insulation Program when it weatherized over 8000 homes near the MSP airport and installed continuously operating exhaust only ventilation in almost all of them. We are known for our extreme winters up here, so the problems we experienced may not show themselves as dramatically in milder locations but the building science is the same. </p>
<p> </p>
<p>When you have a continuously operating fan with a roof termination it WILL melt snow. The snowmelt will add to ice dam problems especially if it runs down onto a valley. We learned pretty quickly to vent out a gable end whenever possible and always stay away from a valley.</p>
<p> </p>
<p>When we installed airtight acoustic storm windows, that are often tighter than the prime window, it can lead to excessive condensation on the upstairs storm window on a two story home. This makes since, right? Air is leaking out on the upper part of the house will leave its moisture on a cold storm window. And believe me, they knew who to call with this problem. Our recommendation was to turn the exhaust ventilation system to high speed. This almost always solved the problem. Why? It was a combination of lowering the humidity in the home (the cold air infiltrating is very dry and ventilation fan is usually in the most used bathroom) and raising the neutral pressure plane to at or above the upstairs window when the fan is at high speed. Less pressure at the window results in less condensation. If the NPP is at or above the window, the storm window will have very little condensation. You are less likely to have attic condensation for these same reasons.</p>
<p> </p>
<p>If you don’t have an airtight connection between the continuously running fans duct and the outside, you will have serious condensation and eventually rot problems with the roof decking. You can also have a buildup of ice between the shingles and the roof termination. We required our installers to use a roof vent termination with a collar on it.</p> John,
I think you're overthin…tag:homeenergypros.lbl.gov,2012-10-04:6069565:Comment:957242012-10-04T17:43:40.998ZRobert Riversonghttp://homeenergypros.lbl.gov/profile/RobertRiversong
<p>John,</p>
<p>I think you're overthinking this passive NPP issue, since it's "passive" only in strictly static conditions, changing all the time under real conditions, and far less important than almost any other design consideration. Active NPP, however, is always worth considering in ventilation system design.</p>
<p></p>
<p></p>
<p></p>
<p>John,</p>
<p>I think you're overthinking this passive NPP issue, since it's "passive" only in strictly static conditions, changing all the time under real conditions, and far less important than almost any other design consideration. Active NPP, however, is always worth considering in ventilation system design.</p>
<p></p>
<p></p>
<p></p> While I agree that "designing…tag:homeenergypros.lbl.gov,2012-10-04:6069565:Comment:958172012-10-04T16:42:16.954ZRobert Riversonghttp://homeenergypros.lbl.gov/profile/RobertRiversong
<p>While I agree that "designing" a passive NPP is an exercise in futility, but designing an active interior pressure balance is an important consideration that is typically overlooked. An exhaust-only ventilation system maintains a more negative interior pressure balance (in relation to outside) and hence reduces dangerous cold weather exfiltration.</p>
<p>And, while we all agree that "natural" (uncontrolled) ventilation is NOT a rational option, there is no reason that Exhaust-Only…</p>
<p>While I agree that "designing" a passive NPP is an exercise in futility, but designing an active interior pressure balance is an important consideration that is typically overlooked. An exhaust-only ventilation system maintains a more negative interior pressure balance (in relation to outside) and hence reduces dangerous cold weather exfiltration.</p>
<p>And, while we all agree that "natural" (uncontrolled) ventilation is NOT a rational option, there is no reason that Exhaust-Only Ventilation can not be a "best practices" approach. One: it's far less expensive both to install and to operate, so it will have wider acceptance. Two: some studies have shown that, with all operating costs considered, including electrical fan consumption and heating/cooling energy impacts, an exhaust-only system can be the least costly to operate - also giving them wider acceptance - while fully meeting ASHRAE IAQ requirements.</p>
<p>Coupling an exhaust-only whole-house fan (which typically is just one of the bathroom fans) with passive make-up air inlets makes it an even better "best practice" approach because it now controls at least most of the infiltration locations, eliminating or reducing that "mouse hole" air.</p>
<p>But you are incorrect, at least in a heating season, that "you are also going to have condensation issues anywhere that the air is coming in", as only exfiltrating air - going from warm to cold - can cause condensation. And condensation does not occur "where the dew point is reached" unless there is a condensing surface (like sheathing). Nor does mold and rot necessarily occur wherever there is condensation - only where the rate of wetting exceeds the rate of drying and there is insufficient moisture buffering.</p>
<p></p>
<p></p>
<p></p> It is always interesting to s…tag:homeenergypros.lbl.gov,2012-10-04:6069565:Comment:959042012-10-04T15:03:00.183ZDon Stevenshttp://homeenergypros.lbl.gov/profile/DonStevens
<p>It is always interesting to see how our fans are installed. This was a good install (except for the new color shingles...) - foamed edges, insulated duct, high rise roof jack, cable ties. The fans come with three spreader bars - a short one for the duct end of the fan and two others for the other end that can telescope to both ceiling joissts or trusses. It is generally OK to just use one of the long hangers to reach one joist, if you are 16" on center and as was done here, but it is a…</p>
<p>It is always interesting to see how our fans are installed. This was a good install (except for the new color shingles...) - foamed edges, insulated duct, high rise roof jack, cable ties. The fans come with three spreader bars - a short one for the duct end of the fan and two others for the other end that can telescope to both ceiling joissts or trusses. It is generally OK to just use one of the long hangers to reach one joist, if you are 16" on center and as was done here, but it is a bit more stable if the two hanger bars are used to reach both joists/trusses, especially for 24" OC..</p> Great, thanks Sean!tag:homeenergypros.lbl.gov,2012-10-03:6069565:Comment:956062012-10-03T01:18:14.042ZPatrick Michaelyanhttp://homeenergypros.lbl.gov/profile/PatrickMichaelyan
<p>Great, thanks Sean!</p>
<p>Great, thanks Sean!</p> It gets the cable tie tightne…tag:homeenergypros.lbl.gov,2012-10-03:6069565:Comment:953842012-10-03T01:08:01.922ZSean Lintow Srhttp://homeenergypros.lbl.gov/profile/sls
<p>It gets the cable tie tightned up properly (i.e. tighter than you can get by hand &amp; prevents it from being able to work loose)</p>
<p>here is one version <a href="http://www.cablemarkers.com/cabletietools.htm">http://www.cablemarkers.com/cabletietools.htm</a></p>
<p>It gets the cable tie tightned up properly (i.e. tighter than you can get by hand &amp; prevents it from being able to work loose)</p>
<p>here is one version <a href="http://www.cablemarkers.com/cabletietools.htm">http://www.cablemarkers.com/cabletietools.htm</a></p> Sean,
Forgive my ignorance,…tag:homeenergypros.lbl.gov,2012-10-03:6069565:Comment:954852012-10-03T00:31:08.279ZPatrick Michaelyanhttp://homeenergypros.lbl.gov/profile/PatrickMichaelyan
<p>Sean,</p>
<p></p>
<p>Forgive my ignorance, but what is a tensioner?</p>
<p></p>
<p>The other brace is obscured in the photo but trust me when I say it is there.</p>
<p></p>
<p>Also, thanks for pointing out the need for another staple.</p>
<p></p>
<p>Patrick</p>
<p>Sean,</p>
<p></p>
<p>Forgive my ignorance, but what is a tensioner?</p>
<p></p>
<p>The other brace is obscured in the photo but trust me when I say it is there.</p>
<p></p>
<p>Also, thanks for pointing out the need for another staple.</p>
<p></p>
<p>Patrick</p>